The subject matter disclosed herein relates to cognitive radio techniques, and more particularly, to systems and methods of using division free duplexing over cognitive radio spectra.
As wireless communication has evolved, the importance of efficient spectral use has become increasingly important. The Federal Communication Commission (FCC) has recognized that while many communication technologies crowd within certain spectral boundaries, many other parts of the radio frequency spectrum are underutilized. Techniques for monitoring spectral usage and opportunistically transmitting across unused frequencies in a way which minimizes interference may be generally referred to as cognitive radio technology. By using spectral awareness, cognitive radio technology may provide more efficient spectral use and improve communication for various wireless technologies.
Cognitive radio spectrum allocation may involve classifications of primary users and secondary users, where the primary user may have superior rights (e.g., via a license) to operate (e.g., transmitting and receiving signals) in an allocated frequency spectrum. Secondary users may operate by sensing spectra that is not in use by a primary user, transmitting over a selected unused frequency spectrum (referred to as a channel), and dynamically altering transmission frequencies during a communication to avoid interferences with primary users, should a primary user enter the selected, previously unused channel. Thus, cognitive radio networks may enable the use of spectrum in an opportunistic manner while avoiding transmission interferences with primary users of the spectrum.
To communicate within a network, cognitive radio devices may establish communication by transmitting and receiving signals with one or more other devices in the network. The ability of two or more communicating devices to meet and establish a link (e.g., a mutual transmitting and receiving of signals) may be referred to as a rendezvous. To operate opportunistically, a secondary user may dynamically sense spectrum use over a potentially large number of channels, and may find a number of channels where a rendezvous can potentially occur. Further, a primary user may be active or become active in any of these channels. Thus, a secondary user should not only establish a rendezvous, but also maintain a rendezvous to minimize interferences with primary users.
Generally, rendezvous schemes involve methods of establishing and maintaining a rendezvous between communicating devices. One type of rendezvous scheme, referred to as aided rendezvous, may involve the use of dedicated control channels for certain devices or clusters of devices (e.g., of a central base station) in a network. As a limited number of control channels are available for establishing a rendezvous between devices, a device may not need to search an unlimited number of channels to rendezvous with another device. However, aided rendezvous schemes may be limited by bottlenecks over common channels and additional complexity and cost in dedicating certain control channels to certain clusters of devices in a network. Another type of rendezvous scheme, referred to as unaided rendezvous or blind rendezvous, may involve allowing all channels to be shared for rendezvous establishment by any device. Blind rendezvous may provide increased channel flexibility, increased scalability and robustness of a network, as well as potentially improved efficiency in channel utilization. However, due to the fact that all channels are potentially available for rendezvous, devices may search a large number of channels over a long amount of time before establishing a rendezvous.